The average speed of Marcella in feet per seconds is 9.5 feet per second.
<h3>How are time taken for travel, distance traveled, and the average speed are related?</h3>
We have this below shown relation between them

For the given case, we have:
The equation
represents the line of best fit for the distance (in feet) that Marcella traveled over time (in seconds)
The line of best fit can be taken as approximately telling about the data points ( y = distance traveled in feet, and x = time spent )
Let the initial time be 'x' with initial distance traveled 'y', then the time after one second will be (x+1), and the distance traveled be 
The value of y and
are calculated as:

Thus, the average speed is calculated at time 'x' as:

We could've also used the fact that in the relation of y to x as
, 'm' denotes the rate of y as x changes.
Thus, the average speed of Marcella in feet per seconds is 9.5 feet per second.
Learn more about average rate here:
brainly.com/question/12322912